The invention relates to a service device for maintenance of a solar panel arrangement and a method for cleaning an inclined surface of a solar panel arrangement.
In the last years, the use of solar panels for the collection of solar energy and conversion into electrical energy has become a common practice. In solar power plants, large numbers of solar panels are mounted on supporting carriers and disposed in an array-like arrangement, usually forming long rows of solar panels neighbouring each other. In order to maximize the yield of collected solar energy, surfaces of the solar panels are aligned towards the sun and therefore inclined with respect to the horizontal. The angle of inclination may be kept fixed during the day, keeping the solar panels in an overall preferred position, or may be maintained in order to follow the sun. Contamination of the solar panel surfaces with dust, sand, snow, leaves and branches of plants, and other residues due to environmental influences are a known problem, causing reduction of the gained electrical energy. Therefore, periodic cleaning of the panel surfaces is necessary in order to achieve a high level of energy production. Besides this, there is further need for maintenance of solar panels especially in solar power plants, e.g. periodic examination of the panels for mechanical or electrical defects. However, manual maintenance like cleaning or examination of a large number of solar panels is costly in terms of time and labour. Furthermore, manual cleaning of solar panel surfaces is tedious work accompanied by physical exhaustion and inattentiveness of the workforce, eventually leading to fluctuations in terms of cleaning and inspection quality.
WO 2008 058 528 A1 describes a washing apparatus for cleaning of solar collectors and solar panels. The washing apparatus comprises an arc-shaped, stiff housing, inside which washing nozzles and brushes are arranged for cleaning a collecting surface of a solar collector. In use, the washing apparatus is mounted from above onto the collecting surface. The washing apparatus housing embraces the solar collector in its edge regions in such a way, that the washing apparatus is guided in a longitudinally movable manner directly on the solar collector. For that purpose, the housing comprises first rollers engaging with the surface to be cleaned and having a rolling axis parallel to the surface as well as second rollers engaging with the edge of the surface and having a rolling axis being perpendicular to the rolling axis of the first rollers. A disadvantage of the described washing apparatus is that due to embracement of the solar panel edges by the housing, the apparatus may be mounted or dismounted to rows of solar collectors only at free ends of the rows, rendering it impossible to mount or dismount the apparatus at arbitrary positions. A further disadvantage is that large masses of pollutants like snow or leaves cannot be handled by the washing apparatus due to the fact that all cleaning takes place in the confined space inside the housing of the apparatus. A further disadvantage with respect to solar panels is that parts of the housing encompass the edges of the surface to be cleaned and therefore may touch the sensitive backsides of solar panels, leading to serious damage of the solar panels.
EP 2 048 455 A2 describes an automatic cleaning system for solar panels. The system comprises longitudinal guiding rails being fixed to a supporting structure of the solar panels and being disposed on opposite sides of the solar panel arrangement to be cleaned. The system comprises further a cleaning brush being disposed orthogonally with respect to the guiding rails. Driving units are provided at both guiding rails for moving the cleaning brush along the guiding rails, thus cleaning the solar panel surfaces. A disadvantage of the described system is that separate, fixedly mounted guiding rails are necessary and that the cleaning brush is fixedly joined to the guiding rails. Accordingly, in a solar power plant comprising a large number of solar panel arrangements, an accordingly large number of guiding rails, driving units and cleaning brushes are necessary for cleaning of all solar panels, leading to high investment costs. Besides cleaning, no further maintenance is feasible with the described system.
EP 0 538 521 A1 describes a cleaning system for roof glazings. The system is designed for the cleaning of atrium-like glazings comprising triangular and trapezium shaped surfaces and pyramid like structures. The cleaning system comprises a first guiding reel being arranged above the glazing surface to be cleaned and a second guiding reel being arranged below the glazing. An extensible brush for cleaning the glazing is guided between the first guiding reel and the second guiding reel. Driving units for driving a corresponding end of the brush along the guiding reel are assigned to each guiding rail. In order to clean e.g. a trapezium shaped window, the window region to be cleaned may be partitioned into a rectangular section and one or two triangular sections. In order to clean the rectangular section, both ends of the brush are driven along the guiding rails in such a way that the brush is oriented perpendicular with respect to the guiding rails. In order to clean a triangular section, one of the ends of the extensible brush is kept in a fixed position, while the other end is driven along the corresponding guiding rail in order to cover the triangular surface. During this movement, the extensible brush changes its length. A disadvantage of the described system is that it comprises fixedly mounted guiding rails and that the cleaning brush is permanently joined to the guiding rails.
DE 10 2006 053 704 A1 considered to be the closest prior art describes a device for maintenance of a solar panel arrangement, comprising a service unit for maintenance of the solar panel arrangement, the service unit bridging the complete width of the solar panel and covering it with a housing. A guiding unit is provided at opposite ends of the housing, each guiding unit being configured as longitudinal groove of the housing extending along the solar panel arrangement and engaging the edge and a rear side of the solar panel arrangement. The service unit comprises a driving unit for moving the service unit along the solar panel arrangement.